1. Field of the Invention
The present invention relates to a fuel injection control apparatus. In particular, the present invention relates to a fuel injection control apparatus for controlling a basic injection quantity of fuel in view of a change in an amount of intake air due to running air.
2. Description of Background Art
In fuel injection control apparatus for calculating a basic injection quantity of fuel from a rotational speed of an engine and a throttle opening, it is known to introduce running air through an intake duct that is open in the direction of travel of a motor vehicle as a means for increasing the torque and horsepower of the engine. For example, an engine control apparatus disclosed in Japanese Patent Laid-open No. 4-342857 determines an engine control quantity, i.e., a fuel injection quantity and a dynamic pressure due to running air introduced from an intake duct that is open in order to introduce the running air. Specifically, in a region where the dynamic pressure is large, i.e., in a region of high vehicle speed or large throttle opening, an incremental fuel quantity correction is carried out depending on the dynamic pressure. The dynamic pressure may be calculated directly by the dynamic pressure detecting means or indirectly from the speed of the vehicle.
The above background art control apparatus determines an engine control quantity that serves as a reference when the dynamic pressure is xe2x80x9c0xe2x80x9d, and corrects the engine control quantity at the dynamic pressure of xe2x80x9c0xe2x80x9d depending on the dynamic pressure when the dynamic pressure is higher than xe2x80x9c0.xe2x80x9d In order to determine an engine control quantity when the dynamic pressure is xe2x80x9c0xe2x80x9d, it is necessary to remove the intake duct and set a reference engine control quantity. However, since air is drawn under different resistances when the intake duct is removed and when the intake duct is attached, it is not possible to accurately set a reference engine control quantity in the control apparatus according to the background art.
The present invention has been made to solve the above objects. Accordingly, it is an object of the present invention to provide a fuel injection control apparatus which is capable of determining a fuel injection quantity as an engine control quantity in view of a dynamic pressure without setting a reference engine control quantity at the dynamic pressure of xe2x80x9c0xe2x80x9d.
To achieve the above object, there is provided in accordance with a first feature of the present invention a fuel injection control apparatus, wherein a basic injection quantity is determined at a first vehicle speed subjected to a dynamic pressure due to running air introduced from an intake duct. A vehicle speed corrective coefficient is set depending on the vehicle speed in order to reduce said basic injection quantity at a second vehicle speed which is lower than said first vehicle speed. According to the first feature, a basic injection quantity is determined while the motor vehicle is running when a dynamic pressure acts thereon, and the basic injection quantity is reduced when no dynamic pressure acts on the motor vehicle.
According to a second feature of the present invention, a throttle corrective coefficient is set so as to have its value reduced as a throttle opening is reduced in a range in which the throttle opening is smaller than a predetermined value. The vehicle speed corrective coefficient is multiplied by the throttle corrective coefficient to correct the basic injection quantity. According to the second feature, the reduction for correction in the basic injection quantity is small in a range of a small throttle opening where the difference of the dynamic pressure between the first vehicle speed and the second vehicle speed is smaller.
According to a third feature of the present invention, the injection quantity is reduced if an engine rotational speed is higher than a predetermined value. According to the third feature, an air-fuel mixture is prevented from being shifted excessively to the lean side when the engine rotational speed is low.
According to a fourth feature of the present invention, the basic injection quantity is reduced and corrected if a gear position is in a predetermined low-speed position. According to the third and fourth features, both the feeling of engine racing at lower speeds and the feeling of engine power in higher gear positions are increased.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.